1. Field of the Invention
The present invention relates to an anode holder, and more particularly to an anode holder for holding an anode in a plating tank used for forming a metal film or an interconnection on a large-scale integrated circuit (LSI) substrate.
2. Description of the Related Art
Recently, a plating process has been employed to form metal films, organic films, interconnections, or bumps (protruding connecting electrode terminals) for semiconductor circuits in a substrate such as a silicon wafer. For example, it has widely been practiced to form bumps of gold, silver, copper, solder, nickel, or multi-layer materials of these metals at predetermined portions on a surface of a semiconductor wafer, which has semiconductor circuits and fine interconnections between the semiconductor circuits, to electrically connect the interconnections via the bumps to electrodes of a package substrate or to tape automated bonding (TAB) electrodes.
Methods of forming interconnections or bumps include various methods, such as electroplating, electroless plating, vapor deposition, and printing. According to a recent tendency to an increased number of I/O terminals in a semiconductor chip and to finer pitches between interconnections, an electroplating method has been employed more frequently because of its capability of fine processing and a high deposition rate. The electroplating method, which is one of the most popular methods of forming interconnections or bumps, can form a metal film having a high purity at a high deposition rate by a relatively simple control.
In an electroplating method, a voltage is applied between an anode and a substrate to form a metal film on a surface of the substrate. The anode serves as an anode terminal for generating an electric current for the plating. The anode is dissolved in a plating solution to supply metal ions into the plating solution in proportion to the amount of plating. Thus, the anode is worn in proportion to the amount of plating. Accordingly, it is necessary to replace anodes periodically.
A conductive portion connecting between an anode and a power source should have a high electric conductivity because such a conductive portion supplies an electric current to the anode for the electroplating. Further, it is important to maintain a sufficient electric connection at a connecting portion between the conductive portion and the anode. Furthermore, it is desirable that the conductive portion connecting between the anode and the power source has a corrosion resistance because the anode is immersed in a plating solution.